(1) Field of the Invention
The present invention relates to an inkjet recording apparatus, particularly to an inkjet recording apparatus that prevents failures of ink-ejection.
(2) Description of the Related Art
A problem of an ink-ejection failure, i.e. failing in normal ejection of ink droplets in an inkjet recording apparatus, is generally known. When an inkjet recording apparatus is used in production of electronic devices and ink-ejection failures occur, a great loss results because the ink-ejection failures are directly linked to production failures. If such ink-ejection failures can be foreseen and prevented, the loss can be avoided.
Relating to the above problem, Japanese laid-open patent publication No. 2004-314459 (hereafter referred to as JP '459) discloses a technique of preventing an ink-ejection failure by projecting the ink-ejection failure, which occurs due to an increase of ink viscosity and entraining of air bubbles into a cavity, from patterns of a pressure vibration by detecting, through a pressure plate, a pressure vibration of the ink within a pressure chamber (referred to as “cavity” in JP '459) in which a pressure for ejecting ink is produced.
One of the causes of the ink-ejection failure is cavitation, which occurs being associated with descending of an ink pressure when a pressure vibration is generated to eject ink. This cavitation occurs under the condition where cores, i.e. the cause of the cavitation, exist within ink and when a pressure of ink remarkably descends.
The art disclosed in JP '459 involves a problem that such ink-ejection failures cannot be prevented due to the reasons described below. In the case that the amplitudes of a pressure vibration that is detected are small even if the cavitation cores exit, this pressure vibration is virtually the same as in the case of non-existence of the cores within the ink. Therefore, the presence of the cores cannot be detected. Even in the case that an amplitude of pressure vibration detected is large, an occurrence of cavitation cannot be projected before the ink is ejected, because the ink as the object to be deleted has been discharge from nozzle.